Pseudomonas aeruginosa causes acute nosocomial pneumonia as well as chronic lung infections in cystic fibrosis patients. The mechanisms responsible for the resulting lung injury remain unclear. Formation of oxidant species such as superoxide and hydrogen peroxide are associated with many forms of lung injury. During the initial funding period of this program, we obtained evidence that three compounds actively secreted by P. aeruginosa damage pulmonary epithelial and endothelial cells via oxidant production. In the next funding period we will define the cellular mechanisms of action of redox cycling. This results in superoxide and hydrogen peroxide generation. Pyocyanin causes a host of deleterious effects on cellular functions both in vitro and in vivo. In spite of this, there is only limited data on the cellular events by cells. Furthermore, the site(s), mechanism(s), and nature of the oxidants produced by pyocyanin, as well as the cellular targets are also poorly understood. We hypothesize that the complex series of effects mediated by pyocyanin occur through its ability to induce site specific oxidant production which leads to the disruption of cellular energy generation and activation of oxidant sensitive signaling pathways. To test this hypothesis three specific aims will be accomplished. Aim 1 is to identify the mechanism(s) of epithelial cell acquisition, cellular trafficking, and metabolism of pyocyanin under in vitro conditions. Aim 2 is to determine how pyocyanin deplete epithelial cells of ATP and cAMP by defining the effects of pyocyanin on oxidative phosphorylation and glycolysis. This aim will also address if pyocyanin acts on oxidant-regulated signaling pathways, IL-8 expression will serve as a model system. The first two aims will use an in vitro system of polarized epithelial cell monolayers using normal and CF cells. Aim 3 will examine the extent to which the in vitro effects of pyocyanin are observed occur under in vivo conditions. This work will focus on IL-8 release and utilize xenografts of human respiratory epithelial cells in SCID mice. These studies will use state of the art technique of cell biology and oxidant chemistry to define novel and previously unexplored mechanisms whereby P. aeruginosa may contribute to acute and/or chronic lung injury.